In contrast to coenzymes, prosthetic groups are

Explanation

Prosthetic groups are non-protein molecules that are covalently attached to an enzyme, making them a permanent part of the enzyme's structure. This is in contrast to coenzymes, which are usually loosely bound and can dissociate from the enzyme. Option A is incorrect because prosthetic groups are not typically derived from vitamins, though some coenzymes are. Option B is incorrect because prosthetic groups are not composed of amino acids; they are usually small organic molecules or metal ions. Option C is incorrect because it describes coenzymes, which are often loosely attached and can easily bind and release from the enzyme.